1. Field of the Invention
The present invention relates to an apparatus for improving serviceability performance of a tall building by making use of the fluctuation of water contained in a water tank, and more particularly to a vibration control apparatus using a water tank located at top floor of a tall building, which serves to reduce excessive lateral vibration of a tall building, especially, for a slender shaped tall building, due to lateral load caused by wind and seismic activity, thereby preventing residents in the tall building from uncomfortable feeling the tall building shaking.
2. Description of the Related Art
In general, as tall buildings tend to become much lighter and higher, vibration problems due to horizontal load caused by wind and seismic activity are on the increase. If residents in the tall buildings feel severe discomfort due to the vibration of the tall buildings, it is clear that the buildings have severe serviceability problems. Therefore, there have been used various solutions for reducing the vibration of the tall buildings.
Such solutions for satisfying design requirements conforming to a desired serviceability performance of the tall buildings include various kinds of vibration control apparatuses. As examples of such vibration control apparatuses, there are a VED (viscoelastic damper), TMD (tuned mass damper), TLD (tuned liquid damper), base isolator, and the like. Although these vibration control apparatuses can be selectively utilized in consideration of their various merits and shortcomings, in reality, all of them cannot be easily applied to tall buildings since they often require an increase in construction costs thus imposing a heavy burden on the building owners.
Considering the TLD installed in the existing tall buildings, since it is separately provided instead of being directly embodied from a water tank previously installed in the tall buildings, the TLD and the water tank tend to duplicate their installation space and load. On account of this problem, in recent years attempts have been made to directly embody the TLD from the elevated water tank. In this case, however, it is necessary to accurately calculate the damping ratio and the damping force which is dependent on the height vibration variation of water contained in the water tank. Furthermore, the TLD directly embodied from the water tank shows a low vibration control capacity, compared with another conventional TLD, which is separately provided along with the water tank. Therefore, the TLD is limitedly used only when it is desired to slightly improve the serviceability of the tall buildings for wind.
In case of the TLD for use in a tall building, which is developed by Samjung construction located in Japan, it comprises a wire mesh, which is vertically installed in the middle of a water tank so as to secure a desired damping ratio by making use of the horizontal resisting force of fluid contained in the water tank. FIG. 1 illustrates the velocity distribution of a fluid flow in a water tank. In FIG. 1, an horizontal fluid flow shows a maximum velocity at the center of the water tank, and a vertical fluid current shows a maximum velocity at the wall surface of the water tank.
FIG. 2 illustrates an example of the vibration control apparatus using a water tank in accordance with the prior art, which is adapted to increase a damping ratio by installing wire meshes at locations where the maximum velocity occurs. That is, as shown in FIG. 2, the rectangular box shaped water tank, designated as reference numeral 1, comprises a plurality of vertical wire meshes 8 arranged side by side in the middle of the water tank 1, a plurality of horizontal wire meshes 5 stacked in multiple layers at both sides of the vertical wire meshes 8, and a pair of water tank covers 9 covering both sides of the top plane of the water tank 1 above the horizontal wire meshes 5.
The vertical wire meshes 8 are concentrically positioned at the middle of the water tank 1, and the horizontal wire meshes 5 located at both sides of the vertical wire meshes 8 are positioned under water or just above the surface of water, thereby serving to increase the damping force in a vertical direction. It should be noted that the water tank shown in FIG. 2 can achieve an effective damping ratio.
Where the water tank 1 is applied to a tall building, however, the horizontal wire meshes 5 cause a great amount of difficulty in their maintenance. Furthermore, in installation, the vertical wire meshes 8 are vertically fitted from the upper side of the water tank 1, which is already constructed, but in case of the horizontal wire meshes 5, it is hard to fit them inside the water tank 1, and to secure a required support strength of connection regions between the vertical and horizontal wire meshes 8 and 5. In order to achieve the required support strength, additional supports should be installed on the middle of the vertical wire meshes 8.
Furthermore, to the vertical and horizontal wire meshes 8 and 5 of the water tank 1 are attached various kinds of floating particles. In this case, usually, the polluted vertical and horizontal wire meshes 8 and 5 are replaced with new ones instead of removing the floating particles from the vertical and horizontal wire meshes, but the horizontal wire meshes 5 cause a great amount of difficulty in the replacement and reconstruction thereof. Due to this difficulty, the vibration control apparatus, using both the vertical and horizontal wire meshes together, is used as a vibration control apparatus itself, without being used as a water tank, resulting in a problem of additional space being required for the installation of a separate water tank.